Regulation of traversing movement of target alignment apparatus

ABSTRACT

Fluid dampers having a predetermined non-linear torque/velocity characteristic are provided for azimuth and elevation axes of a traversing unit for a missile launcher. Each fluid damper comprises a pair of coaxially-aligned, truncated cones formed from metals of different temperature coefficients which regulate the spacing between opposing surfaces of the cones and the thickness of a highly viscous fluid (dimethyl polysiloxane) therebetween to maintain a selected non-linear torque/velocity relationship which provides for limiting of the resistance to torque for rapid slewing to a different sector (target acquisition) while maintaining optimal or critical damping required to prevent overshoot and wavering during tracking of a target throughout the flight of a launched missile.

United States Patent [191 Higginson et al.

[451 May 27, 1975 i 1 REGULATION OF TRAVERSING MOVEMENT OF TARGETALIGNMENT APPARATUS [75] Inventors: Howard P. Higginson; Robert P.

Mack, both of Los Angeles, Calif.

abandoned.

[52] U.S. Cl. 89/37 H [51] Int. Cl F4lf 21/06 [58] Field of Search89/1802, 1.815, 37 B,

89/37 E, 37 H, 40 E, 41 R; 102/3; 188/268, 266, 276; 244/3.1, 3.11,3.12, 3.13, 3.14; 33/344, 364; 248/183; 308/35 [56] References CitedUNITED STATES PATENTS 2,604,163 7/1952 Exline 188/276 2,775,317 12/1956Sinisterra 188/268 2,965,200 12/1960 Pribonic 188/266 2,971,437 2/1961Surtees 244/3.1l 2,998,868 9/1961 Meier 188/266 3,069,783 12/1962Dinsmore 33/364 3,123,330 3/1964 Forbes et a1. 248/183 3,180,603 4/1965OConnor 188/266 3,236,153 2/1966 Newcomb...

3,241,642 3/1966 King 188/268 3,389,637 6/1968 Beler et a1. 89/1.8153,489,087 l/1970 3,552,699 l/1971 3,568,328 3/1971 Sharpe 33/344 FOREIGNPATENTS OR APPLICATIONS 794,301 4/1958 United Kingdom 188/268 OTHERPUBLlCATIONS Laurence W. Spooner, Silicone Putty As An EngineeringMaterial, Product Engineering, Jan. 1950, pp. 90-93.

Primary Examiner-Stephen C. Bentley Attorney, Agent, or FirmRichard J.Rengel; W. H. MacAllister [5 7] ABSTRACT Fluid dampers having apredetermined non-linear torque/velocity characteristic are provided forazimuth and elevation axes of a traversing unit for a missile launcher.Each fluid damper comprises a pair of coaxially-aligned, truncated conesformed from metals of different temperature coefficients which regulatethe spacing between opposing surfaces of the cones and the thickness ofa highly viscous fluid (dimethyl polysiloxane) therebetween to maintaina selected nonlinear torque/velocity relationship which provides forlimiting of the resistance to torque for rapid slewing to a differentsector (target acquisition) while maintaining optimal or criticaldamping required to prevent overshoot and wavering during tracking of atarget throughout the flight of a launched missile.

11 Claims, 5 Drawing Figures PATENTEDFIAY 27 1915 I SHEET REGULATION OFTRAVERSING MOVEMENT OF TARGET ALIGNMENT APPARATUS The invention hereindescribed was made in the course of or under a contract or subcontractthereunder (or grant) with the Department of the Army.

This is a division of copending application Ser. No. 48,787 filed June19, 1970, now abandoned in favor of continuation application Ser. No.343,780, filed Mar. 22, 1973.

BACKGROUND OF THE INVENTION In various equipment requiring sighting ofobjects, substantial damping is required to eliminate waver andovershoot and thereby maintain the equipment sighted directly on targetor other object. In weapon systems, such as a portable missile launcherhaving controlled guidance, optical tracking of the target is providedfor throughout the flight of the missile. Accordingly, it is importantto regulate sighting and tracking movements to eliminate waver of ahuman operator, for example, in order to maintain a true flight paththroughout the flightof the missile. Damping in both azimuth andelevation axes of traversing units of weapon systems and otherequipment, such as television and motion picture cameras, eliminateswaver during tracking and aiming. In guided missile systems, however, itis more important to avoid transmission of, and response to, controlsignals due to waver to eliminate resulting deviations in the missileflight path, particularly near the time of im pact when deviations dueto waver can direct the missile past the target. For example, guidancecontrol signals in response to the waver ofa human operator, typically.6 cycle per second, is capable of causing deviation in the flight ofthe missile being guided such that a moving vehicle at a distance ofonly 50 feet could not be accuratley tracked to score a hit; or astationary target could not be hit at a distance of only 1000 yards.While substantial damping at low traverse rates has been found to benecessary for sighting of this type of equipment, the system isencumbered by an increasing high resistance to motion so as toeffectively limit the traverse rates. During target acquisition, whenrapis slewing about either or both axes is either desirable or requiredin operation, the damping system must be disengaged or an overrideprovided to limit linearly increasing resistance of fluid medium dampers(Newtonian) and the torque required at the higher traverse rates. Thepresent invention overcomes the foregoing and provides other featuresand advantages by regulated non-linear damping for optimal and criticaldamping in the lower range of traverse rates for tracking and sightingwhile limiting the resistance to torque to facilitate tracking at fasterrates and permitting rapid slewing as often required during targetacquisition.

More particularly, in prior weapons sytems of the portable missilelauncher type having controlled guidance and optical tracking of thetarget throughout the flight of the missile, undesirable expedients havebeen employed to avoid the problem encountered in providing ofsubstantial damping to eliminatewaver and overshoot to maintain theequipment cited directly on the target or other object. The automaticmissile guidance system for guiding a missile along the lineof sight toa target established by human operator comprises a guidance unitincluding a radiant energy receiver adapted to receive radiated energyfrom the missile and forming guidance signals related to the deviationof themissile from the line of sight established by the operator by theoptical tracking manually position optical tracker. In US. Pat. No.3,233,847 issued to A. Girsberger on Feb. 8, 1966 which is incorporatedby reference herein, a system is disclosed of the aforementioned typeand which provides for elimination of trembling movements of theoperator as he manipulates the controls. The expedients suggested bythis patent was to provide mechanical drag springs, highly viscousfluids or eddy current brake with a highly damping action, or a low passfilter which could be incorporated in the electrical transmissionchannel for elimination of signals in the undesired frequency range. Asnoted therein, this has the undesirable feature of eliminating large andrapid movements of hand controls into corresponding rapid changes in thecourse of the missile which are often times necessary. In order toprovide for rapid changes in the course of the missileZa system of thisprior patent discloses switches and circuits for combining signals toprovide for rapid changes during certain intervals in the flight of themissile. Accordingly, a compromise has been selected in which onlylimited control of rapid changes is provided during the missile flight.The response time is so degraded by this arrangement that additionalcompensation is provided whenever rapid changes in direction arerequired. Accordingly, direct coupling with the hand controller isprovided for introducing the higher frequency componenets in theirentirety in the coupling between driving and driven shafts is an elasticentrainment wherein the movements of the driven shafts are damped. Otherembodiments relied on a delay in the introduction of control movementsof the hand controls, i.e. only after a time lag by use of drag springswhich provide for retarding changes of azimuth in elevation componentsintroduced by the hand controls.

The present invention overcomes the problems encounted in the systemdisclosed by this patent by providing regulation of traversing movementsin which damping eliminates high frequency vibrations includingtrembling movements or human waver of the operator as he manipulates thecontrols but due to the apparent decrease in viscosity of the damper athigh shear rates provides for rapid movements of the hand controls toprovide corresponding rapid changes of the course of the missile.Critical damping for eliminating human trembling or waver is providedwhile avoiding the difficulties which would otherwise be encountered bylinear increasing damping resistance of Newtonian fluids at slew andtracking rates, by non-linear damping in which limited dampingresistance is provided by the substantial decrease in viscosity at thehigh viscosity of the (nonNewtonian) fluid to avoid the need fordeclutching or changing the damping area.

In US. Pat. No. 2,971,437, issued on Feb. 14, 1961, H. Surtees, amissile guidance system is disclosed in which a tachometer providesacceleration guidance signals for directing a missile in flight.Critical damping of the traversing movement of this system to eliminatehuman waver as provided by the present invention would overcomedifficulties of erratic guidance due to waver of the operator at thecontrols.

SUMMARY OF THE INVENTION The present invention is directed to non-lineardamping of rotational movements about the axes of traversing assembliesof cameras, weapons, and the like to provide a high degree of damping atlow rates of traversals to eliminate waver, jitter and overshoot whileproviding saturation characteristics for rapid slewing at high rates oftraversal during target acquisition. In each of the dampers, a highlyviscous fluid is disposed in a gap between opposing surfaces to induceshear stresses and resistance to relative motion. The proximity of thesesurfaces causes distortion of the fluid and resulting fluid frictiontherein due to shearing stresses. Suspensions and highly viscous fluidshave a complicated response to distortion and the apparent viscositydecreases at higher shear rates which provides for linearly increasingresistance to motion at lower shear rates and limited resistance tomotion at higher shear rates for rapid slewing. For example, an organicfluid, dimethyl polysiloxane of approximately 2 million centistokesviscosity, provides the desired linear increase in resistance foroptimal or critical damping over the range of tracking rates andsaturation in resistance to motion at higher rates of traverse. As aresult of this saturation, the torque required at higher rates oftraverse for rapid slewing is limited whereby the advantage of optimalor critical damping in the lower range of traversal rates is preservedwhile allowing for rapid slewing as either desirable or necessary foroperation.

Regulation of the torque/velocity characteristic of the dampers of thepresent invention is provided by controlling the gap-or spacing betweenopposing cone surfaces and thereby varying the thickness of the fluid tocompensate for variations in viscosity of the fluid due to temperaturevariations. This is important to successful and continuous operation ofthe equipment since the highly viscous fluid cannot be substitutedreadily to provide the desired viscosity nor can the gap width bequickly changed to obtain optimal damping. Compensation for viscosityvariations of 6 to 1 in the fluid in the operating range from 25F to +1F, for example, preserves the desired torque/velocity relationshipincluding optimal or critical damping at the lower traversal rates.

Variation in gap over the range of ambient temperature changes isprovided by an arrangement of inner and outer truncated cones ofdifferent coefficients of expansion in which the gap increases withdecreasing temperatures, i.e. inversely, and at a rate of increase inthe gap which maintains the linear clamping at lower shear rates, andsaturation at the higher shear rates for rapid slewing. Accordingly, itis an object of the present invention to provide a traversing unit forfacilitating acquisition, tracking and aiming of equipment having theforegoing features and advantages.

Another object is the provision of non-linear fluid damping for matchingthe torque/velocity relationship to the different modes of operation ofthe equipment.

A further object is to provide a linear increase in resistance to torquewith an increase in relative motion in the lower range of traversalrates and saturation in resistance to torque at higher rates oftraversal for fast tracking and slewing.

Still another object is the provision of a regulated fluid damperconstruction compensating for changes in viscosity of the damping fluid.

Other objects and features of the invention will become apparent tothose skilled in the art as the disclosure is made in the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a pictorial view ofa missilelauncher having fluid dampers for azimuth and elevational axes of thetraversal unit for illustrating the operation of the nonlinear dampersof the present invention;

FIG. 2 is a perspective view of the azimuth damper assembly of themissile launcher shown in FIG. 1;

FIG. 3 is a cross sectional view of the azimuth damper assembly takenalong the line 33 of FIG. 2;

FIG. 4 is a cross sectional view of the elevation damper assembly of themissile launcher shown in FIG. 1; and

FIG. 5 is a graph illustrating a typical curve of the non-lineartorque/velocity relationship for optimal damping of the preferredembodiment of the invention shown in FIGS. 2 and 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 for amore detailed description of the preferred embodiment of the presentinvention, a portable assault weapon 10 is shown for launching missileswhich are guided to a target 12 by optically tracking a moving targetthroughout the flight of the missile. As indicated, a moving target isacquired in tracking by an operator who applies a lateral force totraversing unit 19 to position a launch tube 14 in azimuth. Controlknobs 17 are rotated to position the launch tube 14 in elevation to viewthe selected target through an optical sight l5 and to center crosshairs on the selected target. In accordance with the preferredembodiment, as illustrated, dampers l6 and 18 are provided on azimuthand elevation axes respectively of the traversing unit 19 for themissile launcher 10. Although the torque/velocity relationship fordamping is nonlinear, it should be noted that for tracking a targetmoving at a constant rate, the operator need only maintain a constantforce on the traversing unit 19 to maintain the target in the opticalsight 15. Having established a force level required, the operator thenmodulates about this level to compensate for small pointing errors. Asindicated in FIG. 5 by the typical curve of the nonlinear torquevelocity relationship for the azimuth damper 16, the required torque toovercome the damping resistance is a function of relative velocity. Thelinear segment of the curve between points A and B is within the rangeof normal target tracking velocities from O to 16 milliradians persecond where there is a high tracking accuracy requirement for the moredistant targets. The slope of the linear portion of the curve isdetermined by matching to the operators performance in maintainingadequate tracking requirements about the azimuth axis. Intermediaterates of 16 to 200 milliradians per second permit the operator to track,with reasonable accuracy, fast crossing, close-in targets. At highertraverse rates above 200 milliradians per second, which are experiencedduring target acquisition and intermediate tracking rates, the slope ofthe curve between points B and C illustrates the limiting of resistanceof the damper 16 and torque required to provide for these tracking ratesincluding rapid slewing of the missile launcher 10 to a new targetsector. The limiting of the damping resistance above tracking rates of16 milliradians per second is a direct result of the apparent decreasein viscosity of the highly viscous fluid (2 million centistokes) at thehigher shear rates. In the lower range of tracking rates, the linearincrease in torque is the expected characteristic of Newtonian fluidsincluding viscous fluids which have appreciable fluid friction. Thehighly viscous fluid has a consistency of a semi-solid at 70F, forexample, and its flow characteristics are not readily evident because ofthe delay in flow.

Referring now to FIGS. 2 and 3, for a detailed description of theazimuth damper assembly 16 of the missile launcher shown in FIG. 1, thetraversing unit 19 shown in FIG. 1, is rotatably supported on a tripodor other mounting arrangement by the azimuth damper 16 shown in FIG. 2.The lower flange 20 of damper 16 is attached to the tripod and isintegral with the inner truncated cone 22 of the damper assembly 16, asshown more clearly in FIG. 3. Outer housing 24, including outertruncated cone 26, is supported for rotation on the inner cone 22 toprovide for a movement of the missile launcher about the azimuth axis. Atachometer including annular members (27, 27a) is seated in an annularcavity 27 and attached to inner and outer cone sections to provide ratesignals for controlling the guidance of launched missiles. In additionto providing traversing damping, the azimuth damper also providesextremely high radial damping between the stator 27a and the rotor 27 ofa DC generator type of tachometer.

In FIG. 3, the highly viscous damping fluid 30 is indicated by sectionlines between inner and outer cones 22 and 26. The damping fluid 30 isretained between opposing annular sections of these cones by annularseals 31 and 32. The inner and outer cones 22 and 26 are formed ofmaterials having different coefficients of expansion to provide spacebetween sections that will increase inversely with temperature, i.e. thethickness of the annular gap dimension is increased to compensate forincreased viscosity of the damping fluid 30 at lower temperatures andvice versa. For example, the outer cone 26 is formed of titanium havinga smaller coefficient of expansion than the inner cone formed ofaluminum to provide for increasing the thickness of the gap betweeninner and outer cones as the ambient temperature decreases and viscosityof the fluid 30 increases, for example. Since the volume of fluidbetween inner and outer cones varies with the thickness of the annulargap, a relative excess of damping fluid 30 is stored, or deficiency ofdamping fluid 30 in the gap is supplied from a bellows reservoir 34. Asrequired therefore, each of the dampers l6 and 18 has a bellowsreservoir which is capable of supplying damping fluid as required tomaintain the annular space or gap filled between opposing annularsections of inner and outer cones 22 and 26. This compensation forviscosity changes of the damping fluid 30 over an ambient temperaturerange of 140F (25F to +115F) maintains the torque/velocity relationshipwithin the desired tolerances, i.e. the curve shown in FIG. 2 is forroom temperature (approximately 70F) and may shift slightly over thetemperature range but the torque required at any given velocity remainswithin the desired tolerances.

Referring to FIG. 4, the elevation damper 18, similar in operation tothe azimuth damper 16 in that the desirable damping features areprovided, is shown in cross section and includes an inner aluminum cone42 and an outer titanium cone 46 providing an annular gap for a highlyviscous fluid 40. In the elevation damper 18, the

inner cone 42 is rotatable about the elevation axis 45 with the launchtube 14*(FIG. 1). The outer cone 46 is secured to the bifurcated housingof the traversing unit 19. The elevation damper I8 is secured to thetraversing unit 19 by suitable fastening means passing through annularflanges47 projecting radially from one end of the outer cone 46. Theinner cone 42, which is supported for rotation about the elevation axisand within the outer cone 46 by annular bearings 47a and 47b as shown,is coupled to a pinion of the launch tube 14 and rotatable therewith. Asshown in FIG. 4, the inner cone 42 is attached to coaxially disposed,annular coupling members 48 and 49 which are secured to the pinionextending from the side of the launch tube 14 to be secured in thecentral openings thereof. The opposite end of the damper 18 is enclosedby a protective cover 41 which is removable to provide access to thedamper interior including viscous fluid outlet 43 and bellows reservoir44. The outlet 43 is sealed by a suitable threaded plug seated in aninterior channel leading to the annular gap between cones. The reservoir44 supplies viscous fluid 40 to the annular gap through an interiorchannel 44a which communicates with fluid stored in a reservoir 44through a threaded tubular coupling 44b. In FIG. 3, corresponding inletand outlet channels 33 and 34a are shown for supplying viscous fluid tothe annular gap of the azimuth damper 16. In addition, azimuth damper 16has provision for passing cables axially through the damper and alocking mechanism 35 for locking the traverse unit 19 securing it fromrotation about the azimuth axis.

As noted earlier, two of the factors affect the rela tionship betweentorque and velocity illustrated by a typical characteristic curve inFIG. 5, namely, the annular gap thickness or spacing between inner andouter cones and the viscosity of the highly viscous fluid. Assuming thetypical damping fluid viscosity to be 2.0 million centistokes, atapproximately F, a spacing of approximately 3.6 mils between inner andouter cones, either damper 16 or 18 will provide the non-linear torquevelocity relationship to the extent necessary to meet performancerequirements of the system. In assembly of the azimuth damper 16 shownin FIG. 3, the gap between inner and outer cones 22 and 26 is adjustedto approximately 3.6 mils by insertion of spacers between opposingjoining surfaces secured by tap screws 36. The thickness of the spacerpositions the inner and outer cones 22 and 26 relative to one anotheralong their common axis to more precisely set the thickness of theannular gap between these cones. The elevation damper 18, shown in FIG.4, provides for adjustment of relative position of the inner cone 42 andouter cone 46 by the placement of spacers between opposing surfaces ofthe peripheral flanges 47.

After assembly of the damper l6 and setting of the gap to the properthickness, as shown in FIG. 3, the highly viscous damping fluid 30 isforced into the gap by supplying the fluid to inlet channel 34a andproducing differential pressure between the inlet 34a and outlet 33. Theelevation damper 18 of FIG. 4 provides for filling the gap 42 withdamping fluid 40 by inlet 44a and outlet 43. The opposing surfaces ofthe inner and outer cones of the respective dampers are wetted by thedamping fluid to produce shear stresses in the fluid upon relativerotation thereof.

As noted earlier, the thickness of the gap of either damper is varied bythe lower coefficient of expansion of the outer cone relative to theinner cone to compen' sate for temperature/viscosity variations. Forexample, the differential in coefficients of expansion of titanium andaluminum is approximately 7.5 X l which provides the desired variationin gap thickness to maintain the torque/velocity relationship withinperformance tolerance requirements. More specifically, the gap thicknessis set at 3.6 mils at the temperature of 70F and due to the differencein coefficients of expansion of titanium and aluminum the gap isincreased in thickness to 4.36 mils at 25F and decreased in thickness to2.6 mils at 125F.

Critical damping is provided in the elevation damper 18 by increasingthe surface areas of the cones 42 and 46. The need for this existsbecause the path of the launched missile is near the earths surface andany slight deviation due to the operators waver, jitter or overshoot intracking or aiming could direct the launched missile into the ground. Inorder that the operator be capable of supplying the larger torquerequired for the critical damping, the control knobs for rotating thelaunch tube 14 about the elevation axis provide a to 1 mechanical ratioby a multiple chain drive coupling the control knobs to the pinions ofthe launch tube 14. The multiple chain drive is disposed inside thetraversing unit 19 and provides a coupling which eliminates backlashfound in other coupling means such as gear train, or compliance found inantibacklash gear trains or cable couplings. The foregoing illustratesthe degree of criticality of the guidance of the missile launcher andfeatures and advantages of the damper of the preferred embodiment of thepresent invention in providing the required non-linear damping about theazimuth and elevation axes.

In light of the above teachings of the preferred embodiments disclosed,various modifications and variations of the present invention arecontemplated and will be apparent to those skilled in the art withoutdeparting from the spirit and scope of the invention.

What is claimed is:

1. In combination, non-Newtonian damped traversing unit and sightingmeans disposed on said traversing unit for locating and trackingobjects;

pivot means providing at least two degrees of movement about azimuth andelevation axes for traversing operations about said axes includingmovement over a range of traversing rates during operation of thetraversing unit;

fluid damper means for respective axes coupled to said pivot means forproducing non-linear dampening of said movement about said axes over therange of traversing rates;

said damper means comprising annular sections having spaced, opposingannular surfaces defining a gap and disposed for relative movementincluding one of said sections which is coupled to said pivot means tobe movable therewith to produce relative movement at a rate which is afunction of said tra-' versing rates;

said damper means including a highly viscous fluid disposed in the gapbetween said sections and engaging the opposing surfaces of the damperto produce shear in said fluid in the range of traverse rates fordamping resistance to relative movement, said highly viscous fluid atthe desired high viscosity and in the range of traversing ratesexhibiting a non-Newtonian characteristic including repeatedlyexhibiting a substantial reduction in apparent viscosity in theintermediate and higher traversing rates of the range of each traversingoperation exceeding predetermined rates of shear to limit the dampingresistance wherein the degree of said reduction is apparent viscosityand limiting of damping resistance is determined by the non-Newtoniancharacteristic of the fluid at the desired high viscosity thereof, saiddamper means being constructed and arranged to utilize the substantialreduction in apparent viscosity provided by the non-Newtoniancharacteristic of the highly viscous fluid in the gap by producingrelative movement of said opposing surfaces including relative movementbelow and above said predetermined shear rates within the range oftraversing rates of the traversing unit to produce non-linearity indamping resistance while maintaining a stable area of fluid contact withthe opposing annular surfaces of the sections forming the gap forproducing a substantial decreasing rate of damping resistance to higherrates of movement producing relative movement of said opposing surfacesabove said predetermined shear rates in the upper range of traversingrates in the operation of said unit wherein said fluid is maderesponsive to relative movement of said annular sections in the range ofshear rates to produce shear stresses in the fluid for non-lineardamping resistance over the range of traversing rates for damping ofmovement of said pivot means about said axis as a function of rate ofmovement so that the resistance to movement is substantially limited tobelow a predetermined torque applied to said pivot means forfacilitating relative movement exceeding a predetermined desiredtraversing rate in said range while maintaining damping resistance belowsaid predetermined desired traversing rate for substantial damping ofmovement of the traversing unit in the lower range of operation thereof.

2. The traversing unit according to claim 1 in which said highly viscousfluid is dimethyl polysiloxane.

3. The traversing unit according to claim 1 in which said fluid has aviscosity of approximately in the range of one to six millioncentistokes, the fluid damper means for said azimuth axis is constructedand arranged to be coupled to said pivot means so that the torquerequired for producing relative movement about the azimuth axis varieslinearly approximately on the order of 3 to foot pounds for traversingrates approximately on the order of 0 to 16 milliradians per second andthe torque is limited to approximately 60 foot pounds for highertraversing rates in the range of traversing rates.

4. The traversing unit according to claim 1 in which the surfaces ofsaid damper means for said azimuth axis, are disposed in close proximityand movement of the pivot means about the azimuth axis is coupled to thedamper means so that relative movement of said surfaces produces shearstresses in said viscous fluid to provide a non-linear torque-velocityrelationship over the range of traversing rates in the operation of thetraversing unit including linearly increasing damping resistance atlower traversing rates and said fluid provides non-linear damping inresponse to linearly increasing friction produced in the fluid filledgap saturating at intermediate shear rates in response to relative movement of said opposing surfaces corresponding to intermediate traversingrates to substantially limit the damping resistance above saidintermediate traversing rates.

5. The traversing unit according to claim 1 in which relative movementof said opposing surfaces of said damper means for said azimuth axis isproduced in response to torque applied to said traversing unit aboutsaid axis and transmitted to at least one of said annular sections andthe gap is filled with fluid and means are provided to maintain the gapfilled with fluid so that the fluid in the gap is made solely responsiveto the rate of relative movement of said surfaces over the range oftraversing rates of the unit to provide a damping resistance which isnon-linear over the operational range of rates of relative movement ofsaid opposing surfaces including linear damping resistance in the regionof lower traversing rates to provide substantial damping resistance toall relative movements at lower traversing rates and limited dampingresistance to movement at intermediate and higher traversing rates.

6. The traversing unit according to claim 1 in which the non-linearityin shear resistance of the damper means is matched to the torquecapabilities of a human operator of the traversing unit, said traversingunit including means for coupling manual movements of the operator toproduce movement about at least one transverse axis.

7. The traversing unit according to claim 1 in which the area ofopposing surfaces of annular sections for damping about the elevationaxis in substantially larger than the area of opposing surfaces of theannular sections for the azimuth axis to provide substantially greaterdamping resistance at lower traversing rates of relative movement of theannular sections for the elevation axis for critical damping about theelevation axis.

8. In combination, sighting means for locating and tracking objectsdisposed on a traversing unit having a plurality of non-linear fluiddampers including dampers for azimuth and elevation axes, each of saiddampers comprising:

damper surfaces disposed in opposing relationship to provide a gapbetween said surfaces;

means for supporting said damper surfaces for relative movement in apredetermined range of operational rates; and

a highly viscous fluid disposed in said gap for fully engaging theopposing damper surfaces over the range of operational rates, said fluidhaving a non- Newtonian characteristic including a non-linear regionexhibiting a substantial apparent decrease in viscosity abovepredetermined shear rates in the range of operation at the highviscosity of the fluid,

said damper surfaces being disposed and arranged to move in said rangeof operational rates and in close proximity so that shearing stressesare produced in the fluid causing said substantial apparent decrease inviscosity at higher rates of relative movement in the range ofoperational rates of the damper, said damper being responsive torelative movement of said damper surfaces to provide a predeterminedsubstantial decrease in rate of increase in damping resistance to saidmovement at higher operational rates of relative movement of the dampersurfaces as a result of a decrease in apparent viscosity of said fluidin the fluid fully engaging the opposing damper surfaces tosubstantially limit the dampening resistance below a predeterminedamount for higher operational rates of movement within said range ofoperational rates of the damper.

9. The non-linear dampers according to claim 8 in which said fluid fillsthe gap and is maintained filled to fully engage the opposing dampersurfaces over the range of operation of the damper and the fluid issemisolid in consistency having a non-Newtonian characteristic in therange of shear rates of operation of the damper so that the resistanceof the damper is substantially limited in the non-linear region of thecharacteristic solely as a result of shear stresses in the fluid in thefluid filled gap.

10. The non-linear dampers according to claim 8 in which said fluidcomprises dimethyl polysiloxane having a viscosity in the range of l to6 million centistokes.

11. In combination, traversing unit having a plurality of damper unitsfor traversing about azimuth and elevation axes and sighting meansdisposed on said traversing unit for locating and tracking objects, eachdamper unit consisting of two parts which can be moved relative to eachother and having mutually opposing surfaces which define a narrow spacecontaining a damping medium of high viscosity; said damper beingcharacterized by the damping medium having a non- Newtonian frictionalresistance in response to shear forces produced in the damping medium inthe narrow space such that the resistance impeding relative movement ofsaid two parts reaches a threshold value at higher speeds of relativemovement; and wherein the area of mutually opposing surfaces of thedamping unit which can be turned relative to each other is considerablylarger for the elevation axis than the area of the mutually opposingsurfaces of the parts which can be turned in relation to each other ofthe unit for the azi-

1. In combination, non-Newtonian damped traversing unit and sightingmeans disposed on said traversing unit for locating and trackingobjects; pivot means providing at least two degrees of movement aboutazimuth and elevation axes for traversing operations about said axesincluding movement over a range of traversing rates during operation ofthe traversing unit; fluid damper means for respective axes coupled tosaid pivot means for producing non-linear dampening of said movementabout said axes over the range of traversing rates; said damper meanscomprising annular sections having spaced, opposing annular surfacesdefining a gap and disposed for relative movement including one of saidsections which is coupled to said pivot means to be movable therewith toproduce relative movement at a rate which is a function of saidtraversing rates; said damper means including a highly viscous fluiddisposed in the gap between said sections and engaging the opposingsurfaces of the damper to produce shear in said fluid in the range oftraverse rates for damping resistance to relative movement, said highlyviscous fluid at the desired high viscosity and in the range oftraversing rates exhibiting a non-Newtonian characteristic includingrepeatedly exhibiting a substantial reduction in apparent viscosity inthe intermediate and higher traversing rates of the range of eachtraversing operation exceeding predetermined rates of shear to limit thedamping resistance wherein the degree of said reduction is apparentviscosity and limiting of damping resistance is determined by thenon-Newtonian characteristic of the fluid at the desired high viscositythereof, said damper means being constructed and arranged to utilize thesubstantial reduction in apparent viscosity provided by thenon-Newtonian characteristic of the highly viscous fluid in the gap byproducing relative movement of said opposing surfaces including relativemovement below and above said predetermined shear rates within the rangeof traversing rates of the traversing unit to produce non-linearity indamping resistance while maintaining a stable area of fluid contact withthe opposing annular surfaces of the sections forming the gap forproducing a substantial decreasing rate of damping resistance to higherrates of movement producing relative movement of said opposing surfacesabove said predetermined shear rates in the upper range of traversingrates in the operation of said unit wherein said fluid is maderesponsive to relative movement of said annular sections in the range ofshear rates to produce shear stresses in the fluid for non-lineardamping resistance over the range of traversing rates for damping ofmovement of said pivot means about said axis as a functiOn of rate ofmovement so that the resistance to movement is substantially limited tobelow a predetermined torque applied to said pivot means forfacilitating relative movement exceeding a predetermined desiredtraversing rate in said range while maintaining damping resistance belowsaid predetermined desired traversing rate for substantial damping ofmovement of the traversing unit in the lower range of operation thereof.2. The traversing unit according to claim 1 in which said highly viscousfluid is dimethyl polysiloxane.
 3. The traversing unit according toclaim 1 in which said fluid has a viscosity of approximately in therange of one to six million centistokes, the fluid damper means for saidazimuth axis is constructed and arranged to be coupled to said pivotmeans so that the torque required for producing relative movement aboutthe azimuth axis varies linearly approximately on the order of 3 to 60foot pounds for traversing rates approximately on the order of 0 to 16milliradians per second and the torque is limited to approximately 60foot pounds for higher traversing rates in the range of traversingrates.
 4. The traversing unit according to claim 1 in which the surfacesof said damper means for said azimuth axis, are disposed in closeproximity and movement of the pivot means about the azimuth axis iscoupled to the damper means so that relative movement of said surfacesproduces shear stresses in said viscous fluid to provide a non-lineartorque-velocity relationship over the range of traversing rates in theoperation of the traversing unit including linearly increasing dampingresistance at lower traversing rates and said fluid provides non-lineardamping in response to linearly increasing friction produced in thefluid filled gap saturating at intermediate shear rates in response torelative movement of said opposing surfaces corresponding tointermediate traversing rates to substantially limit the dampingresistance above said intermediate traversing rates.
 5. The traversingunit according to claim 1 in which relative movement of said opposingsurfaces of said damper means for said azimuth axis is produced inresponse to torque applied to said traversing unit about said axis andtransmitted to at least one of said annular sections and the gap isfilled with fluid and means are provided to maintain the gap filled withfluid so that the fluid in the gap is made solely responsive to the rateof relative movement of said surfaces over the range of traversing ratesof the unit to provide a damping resistance which is non-linear over theoperational range of rates of relative movement of said opposingsurfaces including linear damping resistance in the region of lowertraversing rates to provide substantial damping resistance to allrelative movements at lower traversing rates and limited dampingresistance to movement at intermediate and higher traversing rates. 6.The traversing unit according to claim 1 in which the non-linearity inshear resistance of the damper means is matched to the torquecapabilities of a human operator of the traversing unit, said traversingunit including means for coupling manual movements of the operator toproduce movement about at least one transverse axis.
 7. The traversingunit according to claim 1 in which the area of opposing surfaces ofannular sections for damping about the elevation axis in substantiallylarger than the area of opposing surfaces of the annular sections forthe azimuth axis to provide substantially greater damping resistance atlower traversing rates of relative movement of the annular sections forthe elevation axis for critical damping about the elevation axis.
 8. Incombination, sighting means for locating and tracking objects disposedon a traversing unit having a plurality of non-linear fluid dampersincluding dampers for azimuth and elevation axes, each of said damperscomprising: damper surfaces disposed in opposing relationship to providea gap between Said surfaces; means for supporting said damper surfacesfor relative movement in a predetermined range of operational rates; anda highly viscous fluid disposed in said gap for fully engaging theopposing damper surfaces over the range of operational rates, said fluidhaving a non-Newtonian characteristic including a non-linear regionexhibiting a substantial apparent decrease in viscosity abovepredetermined shear rates in the range of operation at the highviscosity of the fluid, said damper surfaces being disposed and arrangedto move in said range of operational rates and in close proximity sothat shearing stresses are produced in the fluid causing saidsubstantial apparent decrease in viscosity at higher rates of relativemovement in the range of operational rates of the damper, said damperbeing responsive to relative movement of said damper surfaces to providea predetermined substantial decrease in rate of increase in dampingresistance to said movement at higher operational rates of relativemovement of the damper surfaces as a result of a decrease in apparentviscosity of said fluid in the fluid fully engaging the opposing dampersurfaces to substantially limit the dampening resistance below apredetermined amount for higher operational rates of movement withinsaid range of operational rates of the damper.
 9. The non-linear dampersaccording to claim 8 in which said fluid fills the gap and is maintainedfilled to fully engage the opposing damper surfaces over the range ofoperation of the damper and the fluid is semi-solid in consistencyhaving a non-Newtonian characteristic in the range of shear rates ofoperation of the damper so that the resistance of the damper issubstantially limited in the non-linear region of the characteristicsolely as a result of shear stresses in the fluid in the fluid filledgap.
 10. The non-linear dampers according to claim 8 in which said fluidcomprises dimethyl polysiloxane having a viscosity in the range of 1 to6 million centistokes.
 11. In combination, traversing unit having aplurality of damper units for traversing about azimuth and elevationaxes and sighting means disposed on said traversing unit for locatingand tracking objects, each damper unit consisting of two parts which canbe moved relative to each other and having mutually opposing surfaceswhich define a narrow space containing a damping medium of highviscosity; said damper being characterized by the damping medium havinga non-Newtonian frictional resistance in response to shear forcesproduced in the damping medium in the narrow space such that theresistance impeding relative movement of said two parts reaches athreshold value at higher speeds of relative movement; and wherein thearea of mutually opposing surfaces of the damping unit which can beturned relative to each other is considerably larger for the elevationaxis than the area of the mutually opposing surfaces of the parts whichcan be turned in relation to each other of the unit for the azimuthaxis.